Protocols and standards
Group 3
Group 3 is the class of fax machines standardised in 1980, transmitting a page in under a minute over an ordinary telephone line.
It is the generation that made fax universal, and the one every current machine still uses. It fixed what still structures faxing today: pure black-and-white imaging, a standardised line width, and prior negotiation between machines. The earlier, slower analogue groups disappeared with it.